The airport handled 380,584 passengers last month compared to the 360,256 that passed through its facilities in October 2014.
“We are very pleased with October’s numbers for both passenger and cargo activity," enthuses Jess Romo, ONT airport manager.
"Passenger activity was up over 5.5% over last year and cargo remains very strong, with a 10% increase over October 2014.
"The outlook for the last two months of the year is good, and we expect to end the year in positive territory.”
International traffic is maintaining a "vigorous percentage growth, reflecting demand for the Mexican markets", says the airport.
AeroMexico and Volaris served 8,488 passengers, a 17.71% increase over October2014.
Their scheduled service is expected to remain strong through the year.
ONT is located in the Inland Empire, approximately 35 miles east of downtown Los Angeles in the centre of Southern California.
It is a medium-hub, full-service airport with direct commercial jet service to 15 major US cities and connecting service to many domestic and international destinations.